Aircraft fire control computer



4 .Sept E7, 1946. c. G. HoLscHuH ETAL 2,407,665

AIRCRAFT FIRE CONTROL COMPUTER Filed Aug. 1, 1940 5 Sheets-Shet 1 a v Q WFH-FEW@ TRANSMITTER GoNSTn/vr :SPEED Moron IN ENToR Carl l'lolsc 'uh l David Fr l sept. T7, 1946.

c. G..Ho| s'cHuH ETAL AIRCRAFT FIRE CONTROL COMPUTER Filed Aug. 1, 1940l v 3 sheets-sheet 2 Sept W, 3945 C. G. HoLscHUH Ei- Al. 2,407,665

AIRCRAFT FIRE CONTROL COMPUTER Filed Aug. 1, 1940 's sheets-sheet 3 FLIGHT AXIS TARGET WING SPREAD PROJECTED WING SPREAD INVENTORS CARL G. HOLSCHUH DAVID FRAM f ff TH EIR ATTORNEY` Patented Sept. 17, 1946 AIRCRAFT mi: CONTROL COMPUTER Carl G. Holschuh, Wood-Ridge, N. J., and David Fram, Brooklyn, N. Y., assignors to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application August 1, 1940, Serial N0. 349,336

.6 Claims. (Cl. 235-61.5)

This invention relates to apparatus for directing gunfire at an aerial target from an attacking aircraft and refers more particularly to a sighting and computing device adapted to direct gunfire from a high speed pursuit airplane in an attack on a slower plane, for example, a bomber.

The present invention constitutes a modication of and improvement in the apparatus disclosed in the copending application of Earl W. Chafee, Serial No. 211,550, iiled June 3, 1938, and assigned to the assignee of the present inventors, which application discloses an automatic sight and computer comprising apparatus adapted for sighting and tracking an aerial target together with range finding means and a computing mechanism for obtaining from target azimuth, elevation and range data and the indicated air speed of the attacking plane the proper angle for positioning a gun relative to the line of sight. The plan of attack for which the device of the above application is adapted is one in which the ring plane having the superior mobility of the two craft, trails the target on a parallel course and at a chosen range which is maintained constant.

The present invention provides apparatus of the general character previously disclosed which is not limited in its functioning to a single constant range but which has means for obtaining and introducing into the computer variable range data and for performing the more complicated computations incident thereto.

Another object of the present invention is to provide means for setting up and automatically introducing into the computer a rate of change of range.

Still another object is to provide in apparatus of the above character simplified sighting and range nding controls whereby adjustments may be made and automatically continuing changes of adjustment set up without shifting the hand from one control member to another.

A further object is to provide apparatus of the above character which is adapted to be used as a bombsight and also for obtaining a measure of ground speed.

Other objects and advantages of this invention will become apparent as the description proceeds.

Referring to the drawings,

Fig. 1 (in two Parts, Fig. 1A and Fig.lB) is a schematic diagram of an improved sight, range nder and computer according to the invention.

Fig. 2 is a diagram illustrating the method of computing range.

Fig. 3 is a perspective view of the wind resolving unit.

The sighting and computing apparatus is preferably housed in a single housing adapted to be Xedly mounted on an airplane with the axes of the instrument in fixed relationship to, and preferably coincident with, the axes of the plane. The optics of the sighting apparatus comprise a prism I rotatable in azimuth and elevation in which the line of sight experiences one total refiection, a prism 2 in which the line of sight is twice totally reflected, a dove prism 3 rotatable about an inclined axis in which a single reflection occurs, range nding optical wedges 4, 4' and eye piece 5. When a target is in the field of view and a suitable adjustment of the wedges 4, 4' has been made, an observer with his eye placed at Si sees two separate images of the target plane, a normal and a displaced image, these images being upright and unreversed as to right-left components and adjacent Wing tips of the two images apparently just touching one another so that the center to center distance is equal to the wing spread. The positioning of said two images in the just described relationship by the operation of the range setting control or controls eifects a range setting, the value of the range so set being introduced into the computing mechanism.

The training of the line of sight on the target in elevation is accomplished by means of elevation (En) displacement knob 'i and elevation rate knob 8 and in azimuth by means of azimuth (Ao) displacement knob 9 and rate knob lil. The motion of elevation displacement knob 'l is transmitted by spur gears I I and bevel gears I2 to one arm of mechanical differential I3, a second arm of which is connected to shaft I4 which, in turn, is connected by bevel gears I 4 to one arm of mechanical differential I5. A second arm of diierential I5 drives shaft I6 which in turn rotates prism I about horizontal shaft I9 by means of bevel gears I1, worm drive I 8, spur gear Il', freely rotatable about tubular member I5', its meshing pinion I9 and bevel gears I8.

Besides the means for tracking the target in elevation provided by elevation displacement knob l, provision is made for automatic tracking at al constant rate by rotating prism I from the Output of a variable speed device 23 controlled by elevation rate knob 8. The rotation of knob 8 transmitted to shaft 20, rack and pinion 2IA and push rod ZI displaces ball carriage 22 of this device and the position of the balls retained in 'carriage 22 and driven by disc 24, rotated by constant speed motor 25 by way of shaft 2B, determines the speed at which cylinder 2l rotates, this speed being proportional to the displacement of arriage 22 from the center of disc 24. The moion of cylinder 21, introduced into a third arm f differential i3 by way of gearing, results in a ontinuous rotation of shaft i4 and hence of prism about its horizontal axis at a rate proportional o the displacement of knob B. Knobs 1 and 8 are voaxial and are arranged on their shaft and sleeve, yespectively, so that they may be grasped simulaneously with one hand. This is of considerable mportance since by double gripping an operttor with practice can adjust both the. displacenent and rate of change of the line of sight withiut having to shift his hand from one control :nob to another. In order to prevent disturbing '.he position of rate knob 8 whenv displacement rnob lis turned, a detent 23 is provided acting in shaft 2E). Also to prevent rotation of the dis- Jlacement knob by a feed-back of the motion of ;he cylinder 21 through differential I3, a fric- ;ion brake 29 is provided on the displacement drive which provides friction loading for the arm 3f the differential to which the displacement control is connected,

As above mentioned, training of the line of sight on a target in azimuth is accomplished by rotation of azimuth displacement knob 9 and rate knob l0. The rotation of knob 9 is introduced into one arm of mechanical differential 30 by way of spur gears 3l and bevel gears 32, while the output or the motion of a second arm of said differential is transmitted by gearing to shaft 33 and thence by Way of bevel gears 34 to shaft 35 and by another pair of bevel gears 35 to shaft 31. Motion of shaft 31 through gearing 3E! rotates prism l about a vertical axis. In order to prevent the azimuth motion from affecting the elevation setting, the motion of shaft 31 is transmitted by gearing to a third arm of diiferential I which functions as a compensating or unwinding differential. The rotation of shaft 31 also rotates prism 3 by means of gears 38 and thereby prevents the change of position of the image which would otherwise be caused by the rotation of prism l. Azimuth rate control is obtained by an arrangement similar to the elevation rate control. The movement of azimuth rate knob lo is transmitted by shaft 39 and rack and pinion 45 tov ball carriage 4| of variable speed device 42. This device has a disc 43 driven by constant speed motor V25 by way of shaft 26 and a cylinder 44 whose motion is introduced into diiferential 30 by Way of a third arm and appears at the output as a rotation of shaft 33, this motion being combined by the differential with the rotation of displacement knob 9. A detent 45 is provided on rate setting shaft 39 and a friction brake 46 on the displacement drive prevents interaction of the rate and displacement settings, as described in connection with the elevation rate control.

The method of determining range by means of oppositely rotated optical Wedges is fully described in application No. 211.550, previously referred to, and only the present means for eifecting this rotation will be here described. It is assumed that a dimension of the target, for instance, wing spread, is known. This value is set into the sight by adjusting wing spread knob 65 with reference to a suitable scale, not shown.

As described in the above-mentioned application, slant range Do is equal to the target wing spread divided by the product of the sine of the angle through which the optical wedges are displaced and a constant C.

In order to take into consideration a foreshortcned View of the target where the path of the target is offset from that of the pursuit plane, the angle in azimuth the line of sight takes with reference to the longitudinal axis of the pursuit craft is introduced.

Wingspread knob E5 rotates a three-dimensional cam 64 in accordance with target dimensions. The cam is translated by means of gear and rack mechanism 61 which is controlled by gears 5E on shaft 35, the angular displacement of shaft 35 being proportional to the azimuth angle of the line of sight measured from the longitudinal axis of the aircraft. Cam 64 is laid out so that when actuated as just described its lift pin is displaced in proportion to the product of target dimension and the cosine of the angle Ythe line of sight makes with the fore and aft line of the aircraft. The lift pin displacement thus obtained, when divided by the product of the sine of the angle through which the prisms are turned and a constant C is equal to range as explained in detail in the above-mentioned copending application. The latter operation is accomplished byV means of cam which is translated by lift pin 53 of cam 64. Cam 6G is rotated by long pinion 5i and gear 62 driven from shaft 5l which is displaced by a range rate mechanism described further on. The lift pin of cam 6E! is used to effect the range adjustment of the optical wedges, the cam being so laid out that the movement of the lift pin is proportional to the sine of the angle through which the wedges are displaced and the required rotary movement of the cam for this displacement is equal to slant range, Do. Coaxial range displacement and range rate knobs are provided which enable the operator to make range settings in the same manner in which elevation and azimuth settings are made. The motion of range displacement knob 41 by means of spur gears 43 and bevel gears 49 is introduced into mechanical differential 5o by way of one arm and a second arm of the differential is connected by gearing to shaft 5l. Rotation of range rate knob 52, transmitted by way of shaft 53 and rack and pinion 54, displaces ball carriage 55 of variable speed device 55 having disc 51 driven from constant speed moto-r 25 by way of shaft 26 and gearing 58. Cylinder 59 of speed device 56 has imparted to it a rate of rotation proportional to the displacement of ball carriage 55 from the center of disc 51, which motion is introduced into a third arm of differential 50 and appears at the output as a rotation of shaft 5|, the differential combining this motion with that of displacement knob 41.

The relationships of the quantities entering into the computation of range are shown diagrammatically in Fig. 2. It is assumed that the wing spread of the target is known by the operator of the device. In practice he will be provided With a table of wing spreads. Range may therefore be computed. from the projection of this wing spread perpendicular to the line of sight and the angle (0) subtended by this projected wing spread at the sight. Since 6 is usually a small angle, range (Do) is taken to be equal to projected wing spread divided by 0. Projected wing spread is obtained from actual target wing spread by multiplication by the cosine of the azimuth angle (Ao) between the flight axis and the line of sight. t is assumed that the longitudinal axis of the craft coincides with the flight axis, that is, that no side drift occurs. To simplify the figure, since 0 is small, Ao is Shown as the angle between one side of 6 and the flight axis. An approximation of negligible importance is made in showing the base angle of the small right angle triangle which includes wing spread as equal to Ao.

The motie-n of shaft 5|, representing slant range of the target (Do), is transmitted by bevel gears 69 to shafts 'I9 and the former of these two shafts feeding range to azimuth prediction cam 'I9 and by Way of the latter shaft to elevation prediction cam 12.

The means by which motions proportional to the azimuth, elevation and slant range of the target are introduced into the computer have been described. From the rates of change of these quantities and from ballistic data for the projectiles used, the deflection angles of the gun in elevation and azimuth are computed, that is, the angular offsets between the line of sight and axis of the gun bore in two perpendicular planes. Each deection angle is considered as being made up of two parts: (1) the predicted relative angular motion of the target during the flight of the projectile from the gun to the target, and (2) the angular offset necessary to compensate for change of trajectory of the projectile due to wind acting upon it during its time of flight. The wind which deflects the projectile both in azimuth and elevation is considered to be the relative velocity of the airplane and the air and is taken as numerically equal to the indicated air speed (IAS) shown by an air speed meter,

For computing the first part of the elevation deflection angle, rod l2', which is connected to ball carriage 22 and has a displacement proportional to the rate of change of elevation angle, is lcaused to translate three-dimensional cam 'l2 and this cam is rotated in accordance with slant range (Do) from shaft 1| through bevel gears 'i3 and pinion 'I4 meshing with a gear on the cam. The prediction component 'of the elevation deflection angle is equal to the rate of change of elevation angle multiplied by the time of flight (T) of the projectile, and since this time may be taken as a function of range (Do), cam 12 is positioned according to D@ and En rate to obtain as the lift of the follower T5 the prediction angle, that is,

This displacement is introduced by means of rack and pinion 'F6 and shaft 'Il into one arm of mechanical differential 18, a second arm of which is driven in accordance with the second part of the deflection angle, that is, the ballistic correction, determined in a manner described hereinafter.

The azimuth prediction component of the total azimuth deflection angle is obtained in a manner similar to the elevation prediction by translating three-dimensional cam 19 in accordance with rate of change of azimuth angle from push rod 8i) connected to ball carriage 4|. This cam is rotated in accordance with slant range (Do) from shaft 70 by way of bevel gears 8| and pinion 82 which meshes with a gear 0n the cam. The lift of cam follower 83 is the azimuth prediction angle which is introduced into one arm of mechanical differential 84 by way of rack and pinion 85 and shaft 86, a second arm of said differential receiving the azimuth ballistic correction.

For computing the ballistic corrections in elevation and azimuth, indicated air speed (IAS) is introduced into the computer by turning air speed knob 81, geared to a dial 88, to cause an index on said dial to match a corresponding index on a dial 89 actuated by air speed indicator 99. The motion of knob 87 is introduced into air speed resolving unit 9| by way of shaft 92, bevel gears 93, one arm of mechanical differential 94 and shaft 95. This resolving unit Operates on the same principle and may be similar in construction to the resolving unit described in aforementioned application Serial No. 211,550. Fig. 3 of the present application is similar to Fig. 2 of said prior application and illustrates the construction of the resolving unit,

The resolving mechanism as a whole is oriented in azimuth from gun azimuth shaft 96, whose positioning vnll be laterdisclosed, by way of bevel gears 91, shaft 98 and worm 99 meshing with teeth on the periphery of disc or gear 9| on which the mechanism is mounted. The two component velocities into which the air speed is resolved are those in the horizontal plane across and along the line of fire. Shaft 95 which is angularly displaced in accordance with the airspeed, turns shaft |16 through worm drive |15 to position rack bar Il?, by means of pinion |16 engaging a rack thereon, proportionally to air speed. rThe plate 'll' on which bar |'|1 is mounted is movable in guide |l'8' secured to the face of disc 9| and rotating therewith. Plate |11 has a hole engaged by a pin |78 on slider |79. By a. connection to differential 94 the displacement of shaft 98 is combined with that of shaft 92 to remove the effect of the turning of disc 9|', in azimuth, upon the position of shaft 95 and hence upon the radial position of rack bar Differential 913 functions as a compensating differential. The-slider |19 is mounted for transverse movement in a lateral slideway in the vertically movable T-shaped member |39 through which extends an elongated pinion |8| mounted on shaft |83 and meshing with rack teeth |82 on the rear of slider HS. Up and down movement of member |89 is transmitted to a pinion |84 meshing with rack teeth on the rear thereof, the pinion being mounted on shaft lill. It will be apparent that the horizontal wind velocity introduced from shaft |76 is resolved into two components, which, due to the orientation of disc 9|, are head wind and cross wind, referred to the line of re. These components are both functions of the azimuth angle Ag through which disc 9| is turned. The head wind or horizontal component of the air speed along the line of fire is obtained as a rotation of shaft |99, geared to shaft |83, while the component across the line of lire is taken from the resolving unit as a ro'- tation of shaft IUI. Shaft |99, through rack and pinion |92, translates three-dimensional cam |93 which is rotated in accordance with gun or quadrant elevation (corrected for departure from level by means to be described) from shaft |04, Whose positioning will also beV disclosed later. Cam 03 is so laid out that the lift of its follower m5 represents the ballistic correction at a fixed range as a function of wind velocity and elevation angle and to introduce the further factor of variable range, cam pin |05 translates a second three-dimensional cam M36 which is rotated in accordance with slant range (Do) by shaft |97 driven from shaft 5| by bevel gears I B8. The lift of cam follower |99, positioned by cam |06, is the elevation ballistic correction taking into account head wind, quadrant elevation and range. This lift is converted into a rotation by means of rack and pinion |||l and introduced into mechanical differential 'I8 by means of bevel gears actuating one arm of the differential, where it is combined with the elevation prediction introduced by shaft 'l1 and the combined displacement positions one arm of mechanical differential H2, a second arm of which is positioned by cylinder l|3 of variable speed device H, this speed device functioning as a torque amplier.

Torque or force amplification is desirable at this stage of the computing operation since the two components of the deflection angle (prediction and ballistic corrections) are obtained as lifts of cam followers and these followers normally can exert insufcient force to drive the succeeding elements of the computing mechanism. The action of the variable speed device l ill as a torque amplifier is as follows: Disc ||5 is driven at a constant speed from motor 25 by way of shaft 28 and gears lit. The elevation prediction angle introduced into differential T8 as the displacement of shaft 'El and the elevation ballistic correction intro-duced into the same differential by way of bevel gears HI are additively combined by the differential and introduced into one arm of differential ||2 by gear Hl. A second arm of said differential is connected to cylinder H3, while the resultant displacement of the third arm is transmitted by means of rack and pinion H8 and displaces ball carriage H9. Increasing displacement of ball carriage il@ from a central position causes cylinder l i3 to be rotated at an increasing rate until the rotation of the differential shaft mounting gear lll is at the same rate as that of the shaft mounting gear lil by means of which the combined prediction and ballistic corrections are introduced into differential it?. The angular displacement of shaft |25), mounting gear |28 meshing with gear H1', therefore represents the total angular correction, and since the power for driving shaft |20 comes from disc H5 by way of the balls of ball carriage ||9 and cylinder H3, a considerable load may be imposed upon this shaft.V

Shaft |20 by way of bevel gears |2| and shaft f;

|22 drives one arm of mechanical differential |23, a second arm of which is driven from shaft Ul by way of bevel gears |2l and shaft |25. lThe sum of the motions of shafts |25 and appears as the rotation of shaft |26 driven from the third arm of the differential. Since the motion of shaft I4 is proportional to the present elevation angle of the target, the addition of the prediction and ballistic correction angles, i. e., the elevation deflection angle, causes the displacement of shaft |26 to be proportional to the angle at which the gun should be elevated (Eg).

The displacement of the shaft |25 is transmitted by way of bevel gears |21 and shaft |23 to high and low speed gun elevation (Eg) transmitters |29 and |35, respectively. The relative motion of these transmitters is in a ratio determined by the ratio of spur gears ISI, for example 36:1. These transmitters are preferably of the self-synchronous type, that is selsyn transmitters, connected by transmission lines to selfsynchronous receivers |29 and |39 by means of which elevation data is indicated at the gun 260.

For obtaining the ballistic correction in azimuth, the cross wind or wind component across the line of fire is derived from resolving mechanism 9| as the displacement of shaft lill and three-dimensional cam |50 is rotated in accordance therewith. This cam is translated by cam follower |53 which is positioned by a second three-dimensional cam |52. Cam |52 is rotated from shaft lil by way of p-inion |93 and a gear on the cam in accordance with gun elevation (Eg) (corrected for departure of the sight from a level condition) and is translated in accordance with range (3D0) from shaft |61 by way of rack and pinion i511. The lift of follower |5| on cam ll therefore combines functions of cro-ss Wind, elevation and range and represents azimuth ballistic correction which is fed by way of rack and pinion |56, shaft |55, bevel gears |51 and shaft |5d into differential 64, Where it is combined with the azimuth prediction angle to give the total azimuth deflection.

For supplying suicient torque to position succeeding members in accordance with total azimuth deflection angle, variable speed device |39 is connected to operate in a manner similar to variable speed device lid and receives the combined azimuth prediction and ballistic correction angles from differential 3ft by way of differential US5 and transmits this motion as a displacement of shaft HH, bevel gears |42 and shaft |43 to mechanical differential |124, where it is added to the present azimuth of the target, introduced into differential It@ from shaft 33 by Way of bevel gears M5 and shaft |45. The output of differential ifi representing the sum of the present target azimuth and the azimuth deilection angle, i. e., the gun azimuth (Ag), is transmitted by shaft it to high and low speed gun azimuth transmitters H38 and li, respectively, rotating relative to one another at the ratio of gears |41. As in the case of the elevation transmitters, these transmitters are preferably of the self-synchronous or selsyn type adapted to actuate selfsynchronous receivers |48 and Mil' at the gun or guns through suitable transmission lines.

The theory of operation of the computer in computing ballistic correction angles is based on the assumption that the axes of the optical system are truly horizontal and vertical. The effect of head Wind, for example, is computed as a function of the elevation of the gun from the horizontal- If the craft is climbing or diving, its longitudinal axis is tilted relative to the horizontal and the elevation angle fed to the ballistic computing cams, which is an angle measured relative to the craft, cannot be used directly for ballistic correction computation. A correction factor must be introduced and means for introducing this factor are provided by level knob 32 geared to ball level indicato-r |33, having an arcuate tube |34| adapted to be rotated about a horizontal axis parallel to the crafts lateral axis by rotation of knob |32` When the ball indicator |3l is not centralized, thereby indicating that the longitudinal axis of the craft is not horizontal and therefore that the sight is not level, the rotation of knob 32 necessary to bring the ball to a central position is transmitted by wal7 of shaft and bevel gears |35 to mechanical differential |31, where it is added to the gun elevation (Eg) entering the differential from shaft i218 before the combined motion is transmitted to the ballistic cams by shaft |04 and thereby corrects the settings of these cams. It is assumed as before noted that the crafts longitudinal axis coincides with the flight axis, which is the axis along which relative wind acts.

rlhe operation of the device is as follows:

If the sight is not level as shown by the position of the ball of level indicator |33, the operator rst introduces a correction for this condi- 9T tion by rotating level knob |32 to bring the ball indicator |34 back to a central position, and by this operation sets into the ballistic correction computing mechanism a compensating displacement by way of shaft |35, bevel gears |36 and differential |31.

Upon sighting the target, it is assumed the operator will be able to identify the type of plane and from a table of values furnished him the wing spread will be found. This value of wing spread is set into the computing mechanism by rotation of knob 55. At this time a further necessary preliminary operation is the matching of the pointer on dial 88 with the pointer on dial 89 of air speed indicator 9|). The operator then estimates the target azimuth and elevation angles, or a iirst approximation of their values may be obtained from the pilot of the craft Who has before him crossed lines on the front window to aid in estimating these angles. The approximate angles are set by means of elevation displacement knob l and azimuth displacement knob 9, respectively, Upon looking through the sight, the target should then be in the eld of view which, in a preferred form of the invention, may have an angular value of 18.

rlhe target will normally appear to be moving across the field of view and in order to maintain the image or images centralized, the operator will normally nd it necessary to manipulate both displacement and rate knobs, which may be done in the present arrangement by double gripping owing to the proximity of these two knobs and their coaxial arrangement, With practice, although manipulated by one hand, the tWo knobs may be turned independently to a limited but suiiicient extent. If a target is moving at an apparently steady rate across the field of view, the setting up of suitable elevation and azimuth rates will maintain the image centralized once it has been brought to this position by manipulation of t-he two displacement knobs, When the target image remains centered with respect to the cross hairs of reticle E', the operator sets the range by operating range displacement knob 4l until the Wing tips of the two target images touch, as described in aforementioned application No. 211,550.

When the range has been set, the mechanism is in a completely operative condition and correct aiming data is supplied to the gun or guns from elevation transmitters |29 and |30 and azimuth transmitters M8 and |49, When range varies, a constant rate of change of range is set by rotating knob 52 and by double gripping the two range knobs lll and 52, the operator will be able to keep the two images of the optical range finder in their predetermined relative positions indicative of a correct range setting.

Any error in the azimuth and elevation angles transmitted to the gun or guns is directly reflected in ring errors, whereas an error in range introduces only a secondary error in the ballistic and prediction corrections.

By suitable adjustment of the elevation, azimuth and range iinder controls, the apparatus of the present invention may be used to obtain a measure of ground speed and also to establish certain of the angular relationships necessary for aerial bombing, Thus, to use the apparatus as a ground speed measuring device the line of sight is directed vertically downward by rotating prism` about its horizontal axis, and a suitable azimuth angle is set in by rotating the prism about its vertical axis. Images of terrestrial objects 10 may then be caused to remain stationary in the iield of view by setting in the proper elevation rate, from which ground speed may be calculated when altitude is known.

As many changes could bc made in the above construction and many apparently widely diierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. Y

Having described our invention, what we claim and desire to secure by Letters Patent is:

1. Apparatus for compensating for the effect of wind on a shell red from an airplane mounted gun comprising sighting and computing means for determining a line of re to a target which consists of gun elevation and gun azimuth angles, means positioned according to indicated air speed, resolving means actuated thereby and according to the indicated gun azimuth angle for obtaining a measure-of component airspeed in a direction perpendicular to the vertical plane of the gun axis, means providing a measure of target range, a mechanism actuated in acordance with the elevation angle of the gun in said plane and said measures of component wind and range for computing a windage correction to the azimuth aiming angle of the gun, means for regulating the windage correction in proportion to deviation of the airplane from a level course, and means automatically correcting the azimuth angle for the gun relative to the line of sight in accordance with said regulated windage correction.

2. In apparatus for applying a Windage correction to the indicated elevation aiming angle of a line of re of an airplane mounted gun during substantially level flight of the plane, means positioned in accordance with the indicated azimuth aiming angle of the gun relative to a normally horizontal axis of the plane, means positioned in accordance with a measure of the airspeed of the plane as representing relative Wind velocity eiective in deliecting a projectile fired from the gun, means receiving azimuth angle and wind velocity from the first two means and supplying a measure of the horizontal component of wind velocity along the line of re, means positioned in accordance with the indicated gun elevation angle, means providing a measure of target range, means receiving said horizontal component of Wind velocity, gun elevation angle and target range from said several means to eiiect automatically an offset of the indicated and gun angle in elevation, which compensates for the joint effect of said last three received quantities, and means for varying the gun elevation angle received by the last-mentioned means in proportion to inclination of the longitudinal axis of the airplane to correct said oiset when the airplane is not on a truly horizontal course.

3. An apparatus according to claim 1 in which said mechanism is actuated by means comprising a dilerential having a plurality of input arms, one of which is displaced in proportion to the indicated gun elevation angle, and another in proportion to the inclination of the longitudinal axis of the airplane.

4. In apparatus for applying a windage correction to the indicated azimuth aiming angle of a line of fire of an airplane mounted gun during substantially level ilight of the plane, means positioned in accordance with the indicated azi- 11 muth angle of the gun relative to a normally horizontal axis of the plane, means moved in accordance with the airspeed of the plane as rep resenting relative wind velocity effective in delecting a projectile fired from the gun, means receiving said azimuth angle and Wind velocity from said rst two means and supplying as a function or said two quantities a measure of the horizontal component of wind velocity across the line of nre, means positioned in accordance with indicated gun elevation angle, means providing a measure of target range, a mechanism receiving said wind component, gun elevation and target range from said several means and actuating wind correcting apparatus for altering the azimuthaiming angle of the gun in accordance with a function of said three received quantities, means for indicating the inclination of the longitudinal axis of the airplane on departure from level flight, and means adjustable according to the inclination indicating rneans for Proportionately varying the gun elevation angle received by said mechanism whereby a corresponding correction in the azimuth aiming angle is effected.

5. In an inter-plane iire control device for an airplane. mounted gun, a sight having members determining a line o-f sight, means controllable at the sight for simultaneously indicating the angles for. guidance in positioning the guni-n azimuth and elevation deining a line of re and for positioning the line of sig-ht in azimuth and elevation, means movedin` accordance withv a measurev of airspeed of the ring crait, a computing mechanism having means controlled in accorde ance with indicated gun` azimuth and elevation angles and range and the means for setting wind in accordance withv the measured airspeed, said mechanism furtherl including means for deriving from said azimuth and wind settings a head wind component along the line of re and for computingV a wind correction angle in indicated gun ele... vation as a function of said head wind, range, and said elevation angle, together with means automatically relatively offsetting the indicated gun elevation position angle and line of sight in accordance with said computed correction angle, and means for regulating the magnitude of the elevation angle in proportion to the inclination of the longitudinal axis of the firing airplane.

6. In an apparatus for directing fire from a gun mounted on an aircraft and aimed at a target thereby' dening a line of fire, a computing mechanism comprising a irst three-dimensional cam, means for positioning said cam in one dimension controlled in part in accordance With indicated gun elevation (Eg), means for con tinuously positioning the cam in another dimeni sion in accordance with slant range (D0), the last-mentioned means including a variable speed device and a control therefor for obtaining an adjustable constant rate of change of range, a follower for said cam, the cam being so laid out that the lift of the follower is proportional to a ballistic function of elevation and range, a resolving uni-t having an output member, means for adjusting the unit in one sense according to a measure of wind velocity relative to the craft, other means for adjusting the unit in a different sense in accordance With indicated gun position in azimuth whereby the output member is displaced in proportion to the horizontal component of wind velocity across the line of re of the gun, a second three-dimensional cam disposed so as to 15e displaceable in one dimension by the follower of the iirst cam, and in another dimension by the output member of the resolving unit, a follower for the second cam,l said cam being so laid out that its follower is adjusted continuously in proportion to the azimuth correction for the wind component across the line of fire, and gun angle transmitting means operatively connected with the last-mentioned follower.

CARL G. HOLSCHUH. DAVID FRAM. 

